We have obtained strong evidence that the 'second messenger' in the alpha-adrenergic response is Ca ions which is introduced into the cell through the action of the catecholamine. This process will be studied extensively. Experiments will also be performed to see whether the acetylcholine receptor acts similarly in rat parotid gland to introduce Ca ions into the cell. In the pancreas acetylcholine causes enzyme secretion dependent on the presence of Ca ions in the medium. Work will therefore be concerned also with the question whether introduction of Ca ions into pancreas cells by other means will cause enzyme secretion.